End-thrust design for parallel-axis differential

Abstract

Frictional resistance, resulting from end thrust developed by planetary gearing, is appreciably increased to improve control over torque bias characteristics in parallel-axis/torque-proportioning automotive differentials using an unusual planetary combination gear having a first toothed portion which meshes with one of the differential's sun/side gears and a second toothed portion which meshes with a paired combination gear, these first and second toothed portions being separated by a non-meshing portion that "straddles" (i.e., that provides clearance for avoiding contact with) the sun gear that is in mesh with its paired combination gear. In the most preferred embodiments, the second toothed portion of each combination gear is divided into two separate and distinct meshing areas located, respectively, at the gear's outer axial ends. The end faces of the combination gears are used as frictional surfaces for controlling the torque bias of the differential assembly, and a significant measure of control over torque bias is provided by the appropriate selection of the angle and hand of the helically-toothed meshing portions of the sun and planetary combination gears, such tooth designs being selected so that the axial-thrust forces created on the combination gears result in additional frictional resistance.

We claim: 
     
       1. A gear differential for proportioning the torque between a pair of relatively rotating axles at a predetermined torque bias, said differential comprising: a differential housing;   a pair of sun gears positioned in said housing for receiving the ends of said pair of respective axles for rotation therewith about a common axis;   at least one pair of planetary combination gears supported in said housing, each respective combination gear in each said pair having a first toothed portion in meshing engagement with a respective one of said sun gears and having a second toothed portion in meshing engagement with its paired combination gear, the meshing engagement of said sun and combination gears interconnecting said respective axle ends in a mutual driving relationship;   said combination gears being supported in said housing with their respective axes aligned in parallel with the common axis of said sum gears;   said sun and combination gears having helical teeth of predetermined hand selected to develop axial-thrust forces on said combination gears so that the end faces of said combination gears create frictional resistance for controlling the torque bias of the differential assembly; and   said first and second toothed portions of a first one of said combination gears of each said pair being separated by a non-meshing portion that straddles the sun gear that is in mesh with its paired combination gear.   
     
     
       2. The gear differential of claim 1 wherein said first and second toothed portions of said first combination gear of each said pair have tooth designs selected so that the meshing engagement of said second portion with its respective combination gear creates axial-thrust forces in the same direction as the axial-thrust forces created by the meshing engagement of said first portion with its respective sun gear. 
     
     
       3. The gear differential of claim 1 wherein said first and second toothed portions of said first combination gear of each said pair have tooth designs selected so that the axial-thrust forces created by the meshing engagement of said second portion with its respective combination gear do not oppose the axial-thrust forces created by the meshing engagement of said first portion with its respective sun gear. 
     
     
       4. The gear differential of claim 1 wherein said first and second toothed portions of both said combination gears of each said pair are separated by a non-meshing portion that straddles the sun gear that is in mesh with its paired combination gear. 
     
     
       5. The gear differential of claim 4 wherein each of said combination gears includes a third said toothed portion in meshing engagement with its paired combination gear, said second and third toothed portion forming two separate areas at which each combination gear meshes with its paired combination gear. 
     
     
       6. The gear differential of claim 5 wherein said two separated areas at which said of each combination gear meshes with its paired combination gear have tooth designs selected so that the axial-thrust forces created by the meshing engagement of one of said separated areas with its said paired combination gear are in the same direction as the axial-thrust forces created by the meshing engagement of its said first portion with its respective sun gear. 
     
     
       7. The gear differential of claim 5 wherein said two separated areas at which said of each combination gear meshes with its paired combination gear have tooth designs selected so that the axial-thrust forces created by the meshing engagement of said paired combination gears do not oppose the axial-thrust forces created by the meshing engagement of its said first toothed portion with its respective sun gear. 
     
     
       8. The gear differential of claim 1 wherein said sun gears have teeth inclined, respectively, at opposite-handed helical angles meshing with said first toothed portion of said combination gears of each pair, and said separated first and second toothed portions of said first combination gear have helical teeth of the same hand. 
     
     
       9. The gear differential of claim 1 wherein said sun gears have teeth inclined, respectively, at helical angles of the same hand meshing with said first toothed portion of said combination gears of each pair, and said separated first and second toothed portions of said first combination gear have helical teeth of the opposite hand. 
     
     
       10. The gear differential of claim 4 wherein said sun gears have teeth inclined, respectively, at opposite-handed helical angles, and said combination gears of each pair have, respectively, two separated sets of gear teeth having helical angles of the same hand. 
     
     
       11. The gear differential of claim 4 wherein said sun gears have teeth inclined, respectively, at helical angles of the same hand, and said combination gears of each pair have, respectively, two separated sets of gear teeth having helical angles of the opposite hand. 
     
     
       12. The gear differential of claim 4 wherein said paired combination gears are in mesh with each other at two separated areas which straddle the respective positions where each combination gear meshes with its associated sun gear, and said separated areas are positioned, respectively, in proximity to the axial ends of the combination gears. 
     
     
       13. The gear differential of claim 1 wherein said first and second toothed portions, of said combination gear that is paired with said first combination gear, are contiguous. 
     
     
       14. The gear differential of claim 13 wherein said contiguous meshing area of said combination gear is divided into two distinct areas for meshing engagement, respectively, with its said paired combination gear and with its said respective sun gear, said two distinct areas having respective gear tooth designs. 
     
     
       15. The gear differential of claim 5 wherein one of said separated areas at which each pair of combination gears mesh is contiguous with the meshing area in which each said combination gear meshes with its respective sun gear. 
     
     
       16. The gear differential of claim 15 wherein said contiguous meshing area of each combination gear is separated from its other area of meshing engagement with its paired combination gear by a spacing area which provides clearance for avoiding contact with the sun gear associated with its paired combination gear. 
     
     
       17. The gear differential of claim 16 wherein: said sun gears have helical teeth of opposite hand;   said contiguous meshing area of each combination gear is divided into two distinct areas for meshing engagement, respectively, with said paired combination gear and with said respective sun gear, said two distinct areas having respective gear tooth designs; and   said two separated meshing areas where said combination gear meshes with its paired combination gear have helical teeth of same hand.